Non-essential genes in the vaccinia virus HindIII K fragment: a gene related to serine protease inhibitors and a gene related to the 37K vaccinia virus major envelope antigen

AFRC Institute for Animal Health, Houghton Laboratory, Houghton, Huntingdon, Cambridgeshire PE17 2DA, U.K. The complete nucleotide sequence of a cloned copy of the Hin dIII K fragment of the WR strain of vaccinia virus has been determined. Eight open reading frames (ORFs) have been identified, on the basis of size and codon usage. The predicted amino acid sequences of the putative genes have been compared to the Protein Identification Resource and to published vaccinia virus sequences. One gene, predicted to encode a 42.2K protein, is highly related to the family of serine protease inhibitors. It shows approximately 25% identity to human antithrombin III and 19% identity to the cowpox virus 38K protein gene which is also related to serine protease inhibitors. The product of another gene shows a similar high level of identity to the 37K vaccinia virus major envelope antigen. The existence of viable deletion mutants and recombinants containing foreign DNA inserted into both these genes indicates that they are non-essential. Keywords: vaccinia virus, serine protease inhibitors, non-essential genes Received 28 June 1988; accepted 18 August 1988.